/*
 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.util.zip;

/**
 * This class provides support for general purpose compression using the
 * popular ZLIB compression library. The ZLIB compression library was
 * initially developed as part of the PNG graphics standard and is not
 * protected by patents. It is fully described in the specifications at
 * the <a href="package-summary.html#package_description">java.util.zip
 * package description</a>.
 *
 * <p>The following code fragment demonstrates a trivial compression
 * and decompression of a string using <tt>Deflater</tt> and
 * <tt>Inflater</tt>.
 *
 * <blockquote><pre>
 * try {
 *     // Encode a String into bytes
 *     String inputString = "blahblahblah";
 *     byte[] input = inputString.getBytes("UTF-8");
 *
 *     // Compress the bytes
 *     byte[] output = new byte[100];
 *     Deflater compresser = new Deflater();
 *     compresser.setInput(input);
 *     compresser.finish();
 *     int compressedDataLength = compresser.deflate(output);
 *     compresser.end();
 *
 *     // Decompress the bytes
 *     Inflater decompresser = new Inflater();
 *     decompresser.setInput(output, 0, compressedDataLength);
 *     byte[] result = new byte[100];
 *     int resultLength = decompresser.inflate(result);
 *     decompresser.end();
 *
 *     // Decode the bytes into a String
 *     String outputString = new String(result, 0, resultLength, "UTF-8");
 * } catch(java.io.UnsupportedEncodingException ex) {
 *     // handle
 * } catch (java.util.zip.DataFormatException ex) {
 *     // handle
 * }
 * </pre></blockquote>
 *
 * @author David Connelly
 * @see Inflater
 */
public class Deflater {

  private final ZStreamRef zsRef;
  private byte[] buf = new byte[0];
  private int off, len;
  private int level, strategy;
  private boolean setParams;
  private boolean finish, finished;
  private long bytesRead;
  private long bytesWritten;

  /**
   * Compression method for the deflate algorithm (the only one currently
   * supported).
   */
  public static final int DEFLATED = 8;

  /**
   * Compression level for no compression.
   */
  public static final int NO_COMPRESSION = 0;

  /**
   * Compression level for fastest compression.
   */
  public static final int BEST_SPEED = 1;

  /**
   * Compression level for best compression.
   */
  public static final int BEST_COMPRESSION = 9;

  /**
   * Default compression level.
   */
  public static final int DEFAULT_COMPRESSION = -1;

  /**
   * Compression strategy best used for data consisting mostly of small
   * values with a somewhat random distribution. Forces more Huffman coding
   * and less string matching.
   */
  public static final int FILTERED = 1;

  /**
   * Compression strategy for Huffman coding only.
   */
  public static final int HUFFMAN_ONLY = 2;

  /**
   * Default compression strategy.
   */
  public static final int DEFAULT_STRATEGY = 0;

  /**
   * Compression flush mode used to achieve best compression result.
   *
   * @see Deflater#deflate(byte[], int, int, int)
   * @since 1.7
   */
  public static final int NO_FLUSH = 0;

  /**
   * Compression flush mode used to flush out all pending output; may
   * degrade compression for some compression algorithms.
   *
   * @see Deflater#deflate(byte[], int, int, int)
   * @since 1.7
   */
  public static final int SYNC_FLUSH = 2;

  /**
   * Compression flush mode used to flush out all pending output and
   * reset the deflater. Using this mode too often can seriously degrade
   * compression.
   *
   * @see Deflater#deflate(byte[], int, int, int)
   * @since 1.7
   */
  public static final int FULL_FLUSH = 3;

  static {
        /* Zip library is loaded from System.initializeSystemClass */
    initIDs();
  }

  /**
   * Creates a new compressor using the specified compression level.
   * If 'nowrap' is true then the ZLIB header and checksum fields will
   * not be used in order to support the compression format used in
   * both GZIP and PKZIP.
   *
   * @param level the compression level (0-9)
   * @param nowrap if true then use GZIP compatible compression
   */
  public Deflater(int level, boolean nowrap) {
    this.level = level;
    this.strategy = DEFAULT_STRATEGY;
    this.zsRef = new ZStreamRef(init(level, DEFAULT_STRATEGY, nowrap));
  }

  /**
   * Creates a new compressor using the specified compression level.
   * Compressed data will be generated in ZLIB format.
   *
   * @param level the compression level (0-9)
   */
  public Deflater(int level) {
    this(level, false);
  }

  /**
   * Creates a new compressor with the default compression level.
   * Compressed data will be generated in ZLIB format.
   */
  public Deflater() {
    this(DEFAULT_COMPRESSION, false);
  }

  /**
   * Sets input data for compression. This should be called whenever
   * needsInput() returns true indicating that more input data is required.
   *
   * @param b the input data bytes
   * @param off the start offset of the data
   * @param len the length of the data
   * @see Deflater#needsInput
   */
  public void setInput(byte[] b, int off, int len) {
    if (b == null) {
      throw new NullPointerException();
    }
    if (off < 0 || len < 0 || off > b.length - len) {
      throw new ArrayIndexOutOfBoundsException();
    }
    synchronized (zsRef) {
      this.buf = b;
      this.off = off;
      this.len = len;
    }
  }

  /**
   * Sets input data for compression. This should be called whenever
   * needsInput() returns true indicating that more input data is required.
   *
   * @param b the input data bytes
   * @see Deflater#needsInput
   */
  public void setInput(byte[] b) {
    setInput(b, 0, b.length);
  }

  /**
   * Sets preset dictionary for compression. A preset dictionary is used
   * when the history buffer can be predetermined. When the data is later
   * uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
   * in order to get the Adler-32 value of the dictionary required for
   * decompression.
   *
   * @param b the dictionary data bytes
   * @param off the start offset of the data
   * @param len the length of the data
   * @see Inflater#inflate
   * @see Inflater#getAdler
   */
  public void setDictionary(byte[] b, int off, int len) {
    if (b == null) {
      throw new NullPointerException();
    }
    if (off < 0 || len < 0 || off > b.length - len) {
      throw new ArrayIndexOutOfBoundsException();
    }
    synchronized (zsRef) {
      ensureOpen();
      setDictionary(zsRef.address(), b, off, len);
    }
  }

  /**
   * Sets preset dictionary for compression. A preset dictionary is used
   * when the history buffer can be predetermined. When the data is later
   * uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
   * in order to get the Adler-32 value of the dictionary required for
   * decompression.
   *
   * @param b the dictionary data bytes
   * @see Inflater#inflate
   * @see Inflater#getAdler
   */
  public void setDictionary(byte[] b) {
    setDictionary(b, 0, b.length);
  }

  /**
   * Sets the compression strategy to the specified value.
   *
   * <p> If the compression strategy is changed, the next invocation
   * of {@code deflate} will compress the input available so far with
   * the old strategy (and may be flushed); the new strategy will take
   * effect only after that invocation.
   *
   * @param strategy the new compression strategy
   * @throws IllegalArgumentException if the compression strategy is invalid
   */
  public void setStrategy(int strategy) {
    switch (strategy) {
      case DEFAULT_STRATEGY:
      case FILTERED:
      case HUFFMAN_ONLY:
        break;
      default:
        throw new IllegalArgumentException();
    }
    synchronized (zsRef) {
      if (this.strategy != strategy) {
        this.strategy = strategy;
        setParams = true;
      }
    }
  }

  /**
   * Sets the compression level to the specified value.
   *
   * <p> If the compression level is changed, the next invocation
   * of {@code deflate} will compress the input available so far
   * with the old level (and may be flushed); the new level will
   * take effect only after that invocation.
   *
   * @param level the new compression level (0-9)
   * @throws IllegalArgumentException if the compression level is invalid
   */
  public void setLevel(int level) {
    if ((level < 0 || level > 9) && level != DEFAULT_COMPRESSION) {
      throw new IllegalArgumentException("invalid compression level");
    }
    synchronized (zsRef) {
      if (this.level != level) {
        this.level = level;
        setParams = true;
      }
    }
  }

  /**
   * Returns true if the input data buffer is empty and setInput()
   * should be called in order to provide more input.
   *
   * @return true if the input data buffer is empty and setInput() should be called in order to
   * provide more input
   */
  public boolean needsInput() {
    return len <= 0;
  }

  /**
   * When called, indicates that compression should end with the current
   * contents of the input buffer.
   */
  public void finish() {
    synchronized (zsRef) {
      finish = true;
    }
  }

  /**
   * Returns true if the end of the compressed data output stream has
   * been reached.
   *
   * @return true if the end of the compressed data output stream has been reached
   */
  public boolean finished() {
    synchronized (zsRef) {
      return finished;
    }
  }

  /**
   * Compresses the input data and fills specified buffer with compressed
   * data. Returns actual number of bytes of compressed data. A return value
   * of 0 indicates that {@link #needsInput() needsInput} should be called
   * in order to determine if more input data is required.
   *
   * <p>This method uses {@link #NO_FLUSH} as its compression flush mode.
   * An invocation of this method of the form {@code deflater.deflate(b, off, len)}
   * yields the same result as the invocation of
   * {@code deflater.deflate(b, off, len, Deflater.NO_FLUSH)}.
   *
   * @param b the buffer for the compressed data
   * @param off the start offset of the data
   * @param len the maximum number of bytes of compressed data
   * @return the actual number of bytes of compressed data written to the output buffer
   */
  public int deflate(byte[] b, int off, int len) {
    return deflate(b, off, len, NO_FLUSH);
  }

  /**
   * Compresses the input data and fills specified buffer with compressed
   * data. Returns actual number of bytes of compressed data. A return value
   * of 0 indicates that {@link #needsInput() needsInput} should be called
   * in order to determine if more input data is required.
   *
   * <p>This method uses {@link #NO_FLUSH} as its compression flush mode.
   * An invocation of this method of the form {@code deflater.deflate(b)}
   * yields the same result as the invocation of
   * {@code deflater.deflate(b, 0, b.length, Deflater.NO_FLUSH)}.
   *
   * @param b the buffer for the compressed data
   * @return the actual number of bytes of compressed data written to the output buffer
   */
  public int deflate(byte[] b) {
    return deflate(b, 0, b.length, NO_FLUSH);
  }

  /**
   * Compresses the input data and fills the specified buffer with compressed
   * data. Returns actual number of bytes of data compressed.
   *
   * <p>Compression flush mode is one of the following three modes:
   *
   * <ul>
   * <li>{@link #NO_FLUSH}: allows the deflater to decide how much data
   * to accumulate, before producing output, in order to achieve the best
   * compression (should be used in normal use scenario). A return value
   * of 0 in this flush mode indicates that {@link #needsInput()} should
   * be called in order to determine if more input data is required.
   *
   * <li>{@link #SYNC_FLUSH}: all pending output in the deflater is flushed,
   * to the specified output buffer, so that an inflater that works on
   * compressed data can get all input data available so far (In particular
   * the {@link #needsInput()} returns {@code true} after this invocation
   * if enough output space is provided). Flushing with {@link #SYNC_FLUSH}
   * may degrade compression for some compression algorithms and so it
   * should be used only when necessary.
   *
   * <li>{@link #FULL_FLUSH}: all pending output is flushed out as with
   * {@link #SYNC_FLUSH}. The compression state is reset so that the inflater
   * that works on the compressed output data can restart from this point
   * if previous compressed data has been damaged or if random access is
   * desired. Using {@link #FULL_FLUSH} too often can seriously degrade
   * compression.
   * </ul>
   *
   * <p>In the case of {@link #FULL_FLUSH} or {@link #SYNC_FLUSH}, if
   * the return value is {@code len}, the space available in output
   * buffer {@code b}, this method should be invoked again with the same
   * {@code flush} parameter and more output space.
   *
   * @param b the buffer for the compressed data
   * @param off the start offset of the data
   * @param len the maximum number of bytes of compressed data
   * @param flush the compression flush mode
   * @return the actual number of bytes of compressed data written to the output buffer
   * @throws IllegalArgumentException if the flush mode is invalid
   * @since 1.7
   */
  public int deflate(byte[] b, int off, int len, int flush) {
    if (b == null) {
      throw new NullPointerException();
    }
    if (off < 0 || len < 0 || off > b.length - len) {
      throw new ArrayIndexOutOfBoundsException();
    }
    synchronized (zsRef) {
      ensureOpen();
      if (flush == NO_FLUSH || flush == SYNC_FLUSH ||
          flush == FULL_FLUSH) {
        int thisLen = this.len;
        int n = deflateBytes(zsRef.address(), b, off, len, flush);
        bytesWritten += n;
        bytesRead += (thisLen - this.len);
        return n;
      }
      throw new IllegalArgumentException();
    }
  }

  /**
   * Returns the ADLER-32 value of the uncompressed data.
   *
   * @return the ADLER-32 value of the uncompressed data
   */
  public int getAdler() {
    synchronized (zsRef) {
      ensureOpen();
      return getAdler(zsRef.address());
    }
  }

  /**
   * Returns the total number of uncompressed bytes input so far.
   *
   * <p>Since the number of bytes may be greater than
   * Integer.MAX_VALUE, the {@link #getBytesRead()} method is now
   * the preferred means of obtaining this information.</p>
   *
   * @return the total number of uncompressed bytes input so far
   */
  public int getTotalIn() {
    return (int) getBytesRead();
  }

  /**
   * Returns the total number of uncompressed bytes input so far.
   *
   * @return the total (non-negative) number of uncompressed bytes input so far
   * @since 1.5
   */
  public long getBytesRead() {
    synchronized (zsRef) {
      ensureOpen();
      return bytesRead;
    }
  }

  /**
   * Returns the total number of compressed bytes output so far.
   *
   * <p>Since the number of bytes may be greater than
   * Integer.MAX_VALUE, the {@link #getBytesWritten()} method is now
   * the preferred means of obtaining this information.</p>
   *
   * @return the total number of compressed bytes output so far
   */
  public int getTotalOut() {
    return (int) getBytesWritten();
  }

  /**
   * Returns the total number of compressed bytes output so far.
   *
   * @return the total (non-negative) number of compressed bytes output so far
   * @since 1.5
   */
  public long getBytesWritten() {
    synchronized (zsRef) {
      ensureOpen();
      return bytesWritten;
    }
  }

  /**
   * Resets deflater so that a new set of input data can be processed.
   * Keeps current compression level and strategy settings.
   */
  public void reset() {
    synchronized (zsRef) {
      ensureOpen();
      reset(zsRef.address());
      finish = false;
      finished = false;
      off = len = 0;
      bytesRead = bytesWritten = 0;
    }
  }

  /**
   * Closes the compressor and discards any unprocessed input.
   * This method should be called when the compressor is no longer
   * being used, but will also be called automatically by the
   * finalize() method. Once this method is called, the behavior
   * of the Deflater object is undefined.
   */
  public void end() {
    synchronized (zsRef) {
      long addr = zsRef.address();
      zsRef.clear();
      if (addr != 0) {
        end(addr);
        buf = null;
      }
    }
  }

  /**
   * Closes the compressor when garbage is collected.
   */
  protected void finalize() {
    end();
  }

  private void ensureOpen() {
    assert Thread.holdsLock(zsRef);
    if (zsRef.address() == 0) {
      throw new NullPointerException("Deflater has been closed");
    }
  }

  private static native void initIDs();

  private native static long init(int level, int strategy, boolean nowrap);

  private native static void setDictionary(long addr, byte[] b, int off, int len);

  private native int deflateBytes(long addr, byte[] b, int off, int len,
      int flush);

  private native static int getAdler(long addr);

  private native static void reset(long addr);

  private native static void end(long addr);
}
